Yes, you can make wild game sausage without fat. But fat is flavor, and the key is to have the fright amount of fat, which also serves as a binder for the rest of the ingredients. For breakfast and Italian style sausages made from venison, 25 to 30 percent pork fat is about right. It's not an exact science, and most recipes will stipulate how much fat to use. Just bear in mind that too little fat is almost worse than too much. You're making sausage, not tofu bars, so don't be ashamed to lay on the lipids for both moisture content and flavor.